Melt-blown fiber web having improved elasticity and cohesion, and manufacturing method therefor

ABSTRACT

The present invention relates to a melt-blown fiber web having improved elasticity and cohesion, and a manufacturing method therefor. The objective of the present invention is accomplished by a melt-blown fiber web comprising a thermoplastic resin which comprises 10 to 60 wt % of thermoplastic resin microfibers and 40 to 90 wt % of non-circular cross-sectional hollow conjugated staple fibers with respect to the total weight of the fiber web.

TECHNICAL FIELD

The present invention relates to a melt-blown fiber web having improvedelasticity and cohesive strength, and a manufacturing method thereof.

BACKGROUND ART

Indoor noise in internal combustion engine vehicles, ships and aircraftshas been issued. To prevent indoor noise, various sound absorptionmaterials have been produced and marketed.

Melt-blown fiber webs have excellent sound absorption performance andlight unit weight, and thus have been used as sound absorptionmaterials. Such fiber webs can be produced from thermoplastic resin bymelt-blown technology.

Korean Patent Application No. 10-2010-7000497 discloses a porousnonwoven web comprising staple fibers intermingled with melt-blownfibers, wherein the melt-blown fibers comprise a bimodal mixture ofintermingled microfibers and mesofibers, and wherein there are at leastabout five times as many microfibers as mesofibers and wherein themesofibers comprise at least about 30% by weight of the melt-blownfibers.

In addition, Korean Patent No. 0903559 discloses a sound-absorbingnonwoven fabric, which comprises a specific amount of hollow conjugatedstaple fibers uniformly dispersed in a melt-blown nonwoven fabric madeof bicomponent microfibers and has a large surface area per unit weightand good sound absorption performance.

DISCLOSURE Technical Problem

It is an object of the present invention to provide a melt-blown fiberweb which has excellent sound absorption properties and a large specificsurface area, and is light in weight per unit volume so as to be able toincrease the energy efficiency of vehicles, and a production methodthereof.

Another object of the present invention is to provide a melt-blown fiberweb which has excellent elasticity and cohesive strength and also hasexcellent heat insulation properties and noise reduction performance dueto a significantly large number of air layers formed betweenmicrofibers, and which can lead to an increase in energy efficiency, anda production method thereof.

Technical Solution

In order to accomplish the above objects, the present invention providesa melt-blown fiber web consisting of thermoplastic resin, the fiber webcomprising 10-60 wt % of thermoplastic resin microfibers and 40-90 wt %of non-circular cross-sectional hollow conjugated staple fibers withrespect to the total weight of the fiber web.

Preferably, the non-circular cross-sectional hollow conjugated staplefibers have a single fiber fineness of 1-50 denier and a hollow ratio of10% or higher. Preferably, the non-circular cross-sectional hollowconjugated staple fibers are polygonal or tubular in cross section orhave a protrusion/depression pattern at the outer circumferentialportion thereof, and have an enlarged specific surface area.

Preferably, the melt-blown fiber web comprises a horizontal fiber layerand a vertical fiber layer formed on the horizontal fiber layer; thehorizontal fiber layer and the vertical fiber layer are continuouslystacked and connected; and the vertical fiber layer is composed of peaksand valleys, which have a height of 2-50 mm depending on the stackedthickness and are arranged at irregular intervals. Thus, the melt-blownfiber web has excellent elasticity and a high recovery rate.

Preferably, fibers at the top of the vertical fiber layer are entangledwith one another to form the uppermost portion of the waved fiber web.

In addition, the melt-blown fiber web further comprises a coveringfabric composed of a spunbond nonwoven fabric on the upper and lowersurfaces thereof.

In another aspect, the present invention provides a method for producinga melt-blown fiber web, the method comprising the steps of: extruding athermoplastic resin composition through an extruder; spinning theextruded thermoplastic resin composition with a high-temperature andhigh-pressure gas to form thermoplastic resin microfibers; air-blendingthe thermoplastic resin microfibers with non-circular cross-sectionalhollow conjugated staple fibers to form filaments; producing amelt-blown fiber web by forming one portion of the filaments into ahorizontal fiber layer and consecutively forming a vertical fiber layeron the horizontal fiber layer by bringing the other portion of thefilaments into contact with a stack pattern change unit; and winding theproduced melt-blown fiber web.

Advantageous Effects

According to the present invention, the melt-blown fiber web havingimproved elasticity and cohesive strength can be produced byair-blending melt-blown fiber web having specific skeleton withnon-circular cross-sectional hollow conjugated staple fibers having highelasticity and a high hollow ratio.

Further, the melt-blown fiber web according to the present invention canbe produced by a simpler process, has a low density, is more bulky, islight in weight, and has a high compression recovery rate and cohesivestrength, compared to conventional sound absorption materials (PU foam,PET felt, glass fiber, etc.).

In addition, the melt-blown fiber web according to the present inventionmay be used as a sound absorption material or a thermal insulationmaterial.

DESCRIPTION OF DRAWINGS

FIG. 1 is a flow chart showing a method for producing a melt-blown fiberweb according to an embodiment of the present invention.

FIG. 2 is a schematic view showing an apparatus for producing amelt-blown fiber web according to an embodiment of the presentinvention.

FIG. 3 is a schematic cross-sectional view of a melt-blown fiber webaccording to an embodiment of the present invention.

FIG. 4 is an electron micrograph of a melt-blown fiber web according toan embodiment of the present invention.

FIG. 5 is a cross-sectional view of a waved melt-blown fiber webaccording to an embodiment of the present invention.

FIG. 6 shows the results of measuring the sound absorption coefficientof a melt-blown fiber web according to an embodiment of the presentinvention.

FIG. 7 shows the various cross-sections of non-circular cross-sectionalhollow conjugated staple fibers that are used in the present invention.

FIG. 8 is an optical micrograph of non-circular cross-sectional hollowconjugated staple fibers that are used in the present invention.

FIG. 9 is an electron micrograph of the cross-section of non-circularcross-sectional hollow conjugated staple fibers that are used in thepresent invention.

MODE FOR INVENTION

As used herein, the term “thermoplastic resin” refers to a resin thatcan be repeatedly melted at a temperature higher than the melting pointof the polymer resin and solidified by cooling. The thermoplastic resinscan be divided, according to the degree of crystallization, crystallinethermoplastic resins and amorphous thermoplastic resins. The crystallinethermoplastic resins include polyethylene, polypropylene, nylon and thelike, and the amorphous thermoplastic resins include polyvinyl chloride,polystyrene and the like.

As used herein, the term “polypropylene” is intended to encompass notonly homopolymers of propylene, but also copolymers wherein at least 40%of the recurring units are propylene units.

As used herein, the term “polyolefin” is intended to mean any of aseries of largely saturated open-chain polymeric hydrocarbons composedonly of carbon and hydrogen atoms. Typical polyolefins includepolyethylene, polypropylene, polymethylpentene, and various combinationsof ethylene, propylene and methylpentene monomers.

The term “polyester” as used herein is intended to embrace polymerswherein at least 85% of the recurring units are condensation products ofdicarboxylic acids and dihydroxy alcohols with polymer linkages createdby formation of ester units. This includes aromatic, aliphatic,saturated, and unsaturated di-acids and di-alcohols. The term“polyester” as used herein also includes copolymers, blends, andmodifications thereof. A common example of a polyester is polyethyleneterephthalate) (PET) which is a condensation product of ethylene glycoland terephthalic acid.

As used herein, the term “melt-blown microfibers” means the fibers orfilaments formed by extruding a molten melt-processible polymer togetherwith a high-temperature and high-velocity compressed gas through aplurality of fine capillaries. Herein, the capillaries may have variousshapes, including polygonal shapes such as circular, triangular andsquare shapes, and a star shape. For example, the high-temperature andhigh-velocity compressed gas can attenuate the filaments of moltenthermoplastic polymer material to reduce their diameter to about 0.3-10μm. The melt-blown microfibers may be discontinuous fibers or continuousfibers. 70 to 80% or 90% of the melt-blown microfibers may have adiameter of 10 μm or less. Further, 10%, 20% or 30% of the melt-blownmicrofibers may have a diameter of 3 μm or less.

As used herein, the term “spunbond nonwoven fabric” means a fiber webproduced by extruding a molten polymer material through a plurality offine capillaries to form filaments, drawing the filaments throughhigh-temperature tubes and stacking the drawn filaments.

As used herein, the term “non-circular cross-sectional hollow conjugatedstaple fibers” means fibers produced by extruding a bicomponentpolyolefin material through a plurality of fine capillaries to formfilaments and drawing the filaments through high-temperature tubes toform hollow portions. FIG. 7 shows the various cross-sections of thecapillaries. The shape of the capillaries may be any one of polygonalshapes, including a circular shape 501, a triangular shape 502 and apentagonal shape 503. Alternatively, it may also be non-circularcross-sectional cross-sections which have various shapes, such as a starshape 504 or a dumbbell shape 505. Alternatively, the capillaries mayalso have a tubular shape 510 or may have a protrusion/depressionpattern 506 at the outer circumferential portion thereof. Non-circularcross-sectional hollow conjugated staple fibers formed by usingcapillaries having a tubular shape 510 or a protrusion/depressionpattern 506 have an enlarged specific surface area.

The bicomponent materials of polyolefin series may be composed of twoselected from the group consisting of polypropylene, polyethylene,polymethylpentene, nylon, polylactic acid (PLA), andpolytrimethylterephthalate (PTT).

The non-circular cross-sectional hollow conjugated staple fiberspreferably have a single fiber fineness of 1-50 denier, more preferably4-8 denier. Further, the non-circular cross-sectional hollow conjugatedstaple fibers preferably have an average length of 30-60 mm. The crimpof the non-circular cross-sectional hollow conjugated staple fibers isnot artificial, but shows a random curl shape by the intermolecularforce between the two components of the bicomponent material. Further,the non-circular cross-sectional hollow conjugated staple fibers can berestored to their original shape by lightly heating them, and thesurface thereof may also be treated with silk. The non-circularcross-sectional hollow conjugated staple fibers that are used in thepresent invention preferably have a hollow ratio of 10% or higher.Because the non-circular cross-sectional hollow conjugated staple fibersthat are used in the present invention have a non-circular shapedcross-section and a hollow ratio of 10% or higher, these staple fiberscan exhibit high elasticity and a high hollow ratio.

As used herein, the term “nonwoven fabric”, “fiber web” or “nonwovenfabric web” means a structure composed of individual fibers, microfibersor yarns which are arranged without a pattern and in an irregularpattern in contradistinction to knitted fabric to form a planarmaterial.

Hereinafter, the present invention will be described in detail withreference to the accompanying drawings so that it can be easily carriedout by those skilled in the art.

FIG. 1 shows each step of a method for producing a melt-blown fiber webaccording to the present invention.

Specifically, the production method according to the present inventioncomprises the steps of: (S11) extruding a thermoplastic resincomposition through an extruder; (S12) spinning the extrudedthermoplastic resin composition together with a high-temperature andhigh-pressure gas to form microfibers; (S13) air-blending thethermoplastic resin microfibers with non-circular non-circular hollowconjugated staple fibers to form filaments; (S14) stacking one portionof the filaments in a horizontal orientation and in a predeterminedpattern to form a horizontal fiber layer, and stacking a vertical fiberlayer, bringing the other portion of the filaments into contact with astack pattern change unit, to produce a melt-blown fiber web; and (S16)laminating a spunbond nonwoven fabric on the upper and lower surfaces ofthe fiber web.

FIG. 2 schematically shows a fiber web production apparatus that canperform the above production steps.

First, a thermoplastic resin and additives are introduced into anextruder in which they are then kneaded, heated and extruded. Theextruded material is transferred to a spinning die 3, and spun through30-50 orifices in the direction of a collector 13 to form fibers. Duringspinning, a high-temperature and high-velocity gas, injected fromhigh-temperature and high-velocity gas injection holes 4A and 4Bdisposed in the spinning die 3, may be allowed to collide with thefibers, thereby forming melt-blown microfibers 6.

At the same time, non-circular non-circular hollow conjugated fibers maybe supplied to the portion of spinning the melt-blown microfibersthrough a fiber supply unit 10 disposed below the spinning die 3, andmay be air-blended with the melt-blown microfibers.

Herein, the blending may be performed so that the melt-blown fiber webwill comprise 10-60 wt % of the thermoplastic resin microfibers and40-90 wt % of the non-circular non-circular hollow conjugated staplefibers. If the content of the non-circular cross-sectional hollowconjugated staple fibers in the melt-blown fiber web is lower than 40 wt%, the compression recovery rate will be reduced as described inComparative Example 3 (staple fiber content: 25 wt %). If the content ofthe non-circular cross-sectional hollow conjugated staple fibers in themelt-blown fiber web is higher than 90 wt %, the minimum framework ofthe melt-blown fiber web will not be formed, and the microfibers willnot be blended with the non-circular cross-sectional hollow conjugatedstaple fibers, and thus the cohesive strength of the fiber web willdecrease.

50 wt % of the blend of the non-circular cross-sectional hollowconjugated staple fibers and the melt-blown microfibers may directlyreach the collector 13 without passing through a stack pattern changeunit 15, and may be stacked on the collector 13 in a horizontalorientation to form a horizontal layer 10. The remaining 50 wt % of thefibers 11 may pass through the stack pattern change unit 15 to changethe orientation thereof to a vertical orientation, and may be stacked onthe horizontal layer 10 in a vertical orientation to form a verticalfiber layer 20. Herein, the horizontal fiber layer 10 and the verticalfiber layer 20 may also be formed on the same layer, and the verticalfiber layer is continuously stacked on the horizontal fiber layer toform an entangled structure. The vertical fiber layer may be composed ofpeaks and valleys, which have a height of 2-50 mm and are arranged atirregular intervals.

FIG. 5 shows a cross-sectional view of the melt-blown fiber webcomprising the horizontal fiber layer 10 and the vertical fiber layer20. The fibers at the top of the vertical fiber layer 20 may beentangled with one another to form a waved layer 30 that forms theuppermost portion of the fiber web. The waved layer 30 may be configuredsuch that the lines defined by the peaks and valleys of the wave arearranged at irregular intervals in a horizontal direction.

FIG. 3 schematically shows the structure of a melt-blown fiber webaccording to an embodiment of the present invention, and FIG. 4 is ascanning electron micrograph of the cross-section of the melt-blownfiber web. As can be seen in FIGS. 3 and 4, spunbond nonwoven fabrics101A and 101AA are laminated on the upper and lower surfaces of themelt-blown fiber web, and the melt-blown microfibers 102 and theconjugated staple fibers 100 are blended with one another in the fiberweb.

The stack pattern change unit 15 is composed of a steel roll having alength of 2,200 mm and a diameter of 100 pi, a steel roll having thesame size as that of the above steel roll, and a stainless steel meshbelt connected to the rolls and having a diameter of 2,100 mm. Thedistance between the steel rolls is 400 mm, and the two steel rolls arerotated in the same direction at the same speed. In addition, inside ofthe mesh belt may include an absorption unit configured to absorb thehigh-temperature and high-pressure gas injected from the spinning die 3.The vertical distance between the stack pattern change unit 15 and thespinning die 3 is preferably 40% longer than the distance between thestack pattern change unit 15 and the collector 13. At this distance, 50wt % of the melt-blown microfibers, spun from the spinning die andair-blended with the non-circular cross-sectional hollow conjugatedstaple fibers, can be collected.

Hereinafter, the present invention will be described in detail withreference to examples, but the scope of the present invention is notlimited to these examples.

Example 1

A thermoplastic resin composition comprising 99.8 wt % of homopropyleneH7914 polymer resin (LG Chemical Ltd.) having a melt index of 1400 g/10min (230° C.), 0.01 wt % of UV stabilizer Tinuvin 622 (Ciba SpecialChemical) and 0.01 wt % of thermal stabilizer Irganox 1010 was fed intoan extruder. The single extruder having an L/D ratio of 1/28 was rotatedat 80 rpm to knead, heat and extrude the thermoplastic resincomposition. Then, the kneaded composition was transferred to thespinning die 3, and spun in the direction of the collector 13 through 32orifices (orifice diameter: 0.2 mm) per inch to form spun fibers. Duringspinning, a high-temperature and high-velocity gas, injected from ahigh-temperature and high-velocity gas injection holes 4A and 4B formedin the spinning die 3, was allowed to collide with the fibers, therebyproducing melt-blown microfibers 6 made of polypropylene and having anaverage thickness of 3 μm.

At the same time, polyolefin-based non-circular cross-sectional hollowconjugated staple fibers 5 (Huvis Co., Ltd.; X94, X01 or N368), havingan average thickness of 6 denier and an average length of 40 mm andcomprising a silk-treated surface, were supplied through the conjugatedfiber supply unit 10 to the portion to which the melt-blown microfiberswere spun and in which the melt-blown microfibers 6 were air-blendedwith the non-circular cross-sectional hollow conjugated staple fibers 5.

Herein, the melt-blown microfibers and the non-circular cross-sectionalhollow conjugated staple fibers were blended at a weight ratio of 50:50.

50 wt % of the melt-blown fibers 11 were allowed to directly reach thecollector 13 without passing through the stack pattern change unit 15,and were stacked on the collector 13 in a horizontal orientation. Theremaining 50 wt % of the melt-blown fibers 11 were passed through thestack pattern change unit 15 to change the orientation of the fibers 11to a vertical orientation, and were stacked on the horizontally orientedmelt-blown fiber web in a vertical orientation.

The melt-blown fiber web 12 produced as described above had a weight of300 g/m², and was wound in a winding machine 14 to have a width of 1,800mm and a length of 50 m.

Spunbond nonwoven fabrics 101A and 101AA were laminated on both surfacesof the wound fiber web, thereby producing a melt-blown fiber web havinga total weight of 330 g/m² and a thickness of 35 mm.

Example 2

A melt-blown fiber web was produced in the same manner as described inExample 1, except that melt-blown microfibers and non-circularcross-sectional hollow conjugated staple fibers were used at a weightratio of 40:60 and that the melt-blown fiber web 12 laminated with thespunbond nonwoven fabrics had a total weight of 330 g/m² and a thicknessof 35 mm.

Example 3

A melt-blown fiber web was produced in the same manner as described inExample 1, except that melt-blown microfibers and non-circularcross-sectional hollow conjugated staple fibers were used at a weightratio of 20:80 and that the melt-blown fiber web 12 laminated with thespunbond nonwoven fabrics had a total weight of 120 g/m² and a thicknessof 12 mm.

Example 4

A melt-blown fiber web was produced in the same manner as described inExample 1, except that melt-blown microfibers and non-circularcross-sectional hollow conjugated staple fibers were used at a weightratio of 20:80 and that the melt-blown fiber web 12 laminated with thespunbond nonwoven fabrics had a total weight of 190 g/m² and a thicknessof 18 mm.

Comparative Example 1

A thermoplastic resin composition comprising 99.8 wt % of homopropyleneH7914 polymer resin (LG Chemical Ltd.) having a melt index of 1400 g/10min (230° C.), 0.01 wt % of UV stabilizer Tinuvin 622 (Ciba SpecialChemical) and 0.01 wt % of thermal stabilizer Irganox 1010 was fed intoan extruder. The single extruder having an L/D ratio of 1/28 was rotatedat 80 rpm to knead, heat and extrude the thermoplastic resincomposition. Then, the kneaded composition was transferred to thespinning die 3, and spun in the direction of the collector 13 through 32orifices (orifice diameter: 0.2 mm) per inch to form spun fibers. Duringspinning, a high-temperature and high-velocity gas, injected from ahigh-temperature and high-velocity gas injection holes 4A and 4B formedin the spinning die 3, was allowed to collide with the fibers, therebyproducing melt-blown microfibers 6 made of polypropylene and having anaverage thickness of 3 μm. The spun melt-blown microfibers directlyreached the collector and were stacked thereon. The stacked fiber webwas wound in a winding machine, and then spunbond nonwoven fabricshaving a weight of 15 g/m² were laminated on both surfaces of the woundfiber web, thereby producing a polypropylene melt-blown fiber webcomprising 100 wt % of polypropylene melt-blown microfibers and having atotal weight of 330 g/m² and a thickness of 20 mm.

Comparative Example 2

A thermoplastic resin composition comprising 99.8 wt % of homopropyleneH7914 polymer resin (LG Chemical Ltd.) having a melt index of 1400 g/10min (230° C.), 0.01 wt % of UV stabilizer Tinuvin 622 (Ciba SpecialChemical) and 0.01 wt % of thermal stabilizer Irganox 1010 was fed intoan extruder. The single extruder having an L/D ratio of 1/28 was rotatedat 80 rpm to knead, heat and extrude the thermoplastic resincomposition. The kneaded composition was transferred to the spinning die3, and spun in the direction of the collector 13 through 32 orifices(orifice diameter: 0.2 mm) per inch to form spun fibers. Duringspinning, a high-temperature and high-velocity gas, injected from ahigh-temperature and high-velocity gas injection holes 4A and 4B formedin the spinning die 3, was allowed to collide with the fibers, therebyproducing melt-blown microfibers 6 made of polypropylene and having anaverage thickness of 3 μm.

At the same time, polyethylene terephthalate staple fibers were suppliedthrough the conjugated fiber supply unit 10 to the portion to which themelt-blown microfibers were spun and in which the melt-blown microfibers6 were air-blended with the non-circular cross-sectional hollowconjugated staple fibers 5.

The melt-blown fiber web 12 produced as described above had a weight of300 g/m², and was wound in a winding machine 14 to have a width of 1,800mm and a length of 50 m. Spunbond nonwoven fabrics were laminated onboth surfaces of the wound fiber web, thereby producing a melt-blownfiber web having a total weight of 330 g/m² and a thickness of 35 mm.

Comparative Example 3

A fiber web was produced in the same manner as described in ComparativeExample 2, except that polypropylene melt-blown microfibers and generalhollow staple fibers made of polyethylene terephthalate (PET) were usedat a weight ratio of 75:25. The produced fiber web had a total weight of190 g/m² and a thickness of 8 mm.

Comparative Example 4

A fiber web was produced in the same manner as described in ComparativeExample 2, except that polypropylene melt-blown microfibers and generalhollow staple fibers made of polyethylene terephthalate (PET) were usedat a weight ratio of 60:40. The produced fiber web had a total weight of190 g/m² and a thickness of 10 mm.

Test Example

The thickness, compression recovery rate, cohesive strength, soundabsorption coefficient and thermal resistance value of each of the fiberwebs produced in the Examples and the Comparative Examples weremeasured, and the results of the measurement are shown in Tables 1 to 5below. FIG. 6 shows the results of measuring the sound absorptioncoefficients of the fiber webs of Example 1 (a), Example 2 (b),Comparative Example 1 (c) and Comparative Example 2 (d).

The thicknesses of test samples were measured in accordance with Article5.3 of International Standard ISO 9073-2. The thickness of each testsample was measured, and the average value thereof was recorded as arepresentative value.

In order to measure the compression recovery rate of test samples, fivesquare test samples, each having a size of 100 mm×100 mm, were collectedfrom any positions. Each of the collected samples was pressed with apressure of 0.1 kPa using 150 g of a square pressing plate having a sizeof 120 mm×120 mm, and then the thickness of each sample beforecompressing was measured with a ruler. To compress each test sample,each sample was placed under a steel plate having dimensions of 100mm×100 mm×0.8 mm, and a 40 pi weight was placed thereon and allowed tostand at 120±2° C. for 1 hour, after which the thickness of each sampleafter compression was measured. The difference between the thicknessbefore compression and the thickness after compression was calculated,and then the average value was recorded as a representative value.

The cohesive strength of test samples was measured in accordance withGMW 14695. Specifically, both surfaces of each fiber web were pulled ata speed of 25 mm per minute, and the maximum load at which the cohesionof each fiber web was broken was measured.

To measure the sound absorption performance of test samples, the soundabsorption coefficients of test samples, each having a size of1,000×1,200 mm, were measured by the small scale reverberation chambermethod in accordance with technical standard GM 14177.

The thermal resistance values (clo) of test samples were measured inaccordance with KS K 0466.

The results of the tests are shown in Tables 1 to 5 below.

TABLE 1 Thickness Test sample Thickness (mm) Example 1 35 Example 2 35Example 3 12 Example 4 18 Comparative Example 1 20 Comparative Example 235 Comparative Example 3 8 Comparative Example 4 10

TABLE 2 Compression recovery rate (thermal resistance: compressed at 120± 2° C. for 1 hour) Compression recovery Test sample rate (%) Example 165 Example 2 70 Example 3 80 Example 4 80 Comparative Example 1 40Comparative Example 2 55 Comparative Example 3 50 Comparative Example 460

TABLE 3 Cohesive strength Cohesive Test sample strength (N/cm²) Example1 51 Example 2 53 Example 3 54 Example 4 56 Comparative Example 1 40Comparative Example 2 46 Comparative Example 3 43 Comparative Example 445

TABLE 4 Sound absorption coefficient 400 500 630 800 1k 1.25k 1.6k 2k2.5k 3.15k 4k 5k 6.3k 8k 10k NRC Example 1 0.38 0.56 0.73 0.89 1.00 1.051.02 1.01 1.02 1.00 1.00 0.99 0.99 1.02 1.05 0.89 Example 2 0.41 0.590.75 0.91 1.05 1.10 1.08 1.06 1.05 1.01 1.02 1.04 1.06 1.08 1.13 0.93Comp. 0.17 0.30 0.41 0.51 0.64 0.76 0.82 0.86 0.85 0.85 0.80 0.78 0.760.79 0.84 0.65 Example 1 Comp. 0.25 0.41 0.56 0.71 0.83 0.98 1.01 1.001.00 0.96 0.94 0.95 0.96 0.97 0.99 0.79 Example 2

TABLE 5 Thermal resistance value Thermal Test sample resistance (clo)Example 3 2.507 Example 4 4.207 Comparative Example 1 1.921 ComparativeExample 2 2.310

As can be seen from the test results in the Tables, the fiber webproduced in Example 1 of the present invention showed an increase insound absorption coefficient of about 27%, an increase in compressionrecovery rate of about 25%, and an increase in cohesive strength ofabout 22%, compared to the fiber web of Comparative Example 1.

In addition, the fiber web of Example 1 showed an increase in soundabsorption coefficient of about 12%, an increase in compression recoveryrate of about 10%, and an increase in cohesive strength of about 10%,compared to the fiber web of Comparative Example 2.

The fiber web of Example 2 showed an increase in sound absorptioncoefficient of about 4%, an increase in compression recovery rate ofabout 5%, and an increase in cohesive strength of about 4%, compared tothe fiber web of Example 1.

The fiber web of Example 3 showed an increase in thermal resistancevalue of about 30% compared to the fiber web of Comparative Example 3,and the fiber web of Example 4 showed an increase in thermal resistancevalue of about 82% compared to the fiber web of Comparative Example 4.

Taking the test results together, it can be seen that the melt-blownfiber web of the present invention, which is produced by air-blendingmelt-blown microfibers with non-circular cross-sectional hollowconjugated staple fibers and has a fiber web framework formed bystacking the horizontal fiber layer and the horizontal fiber layer, hasexcellent sound absorption performance and high thermal resistancevalues, because it has an enlarged specific surface area and includes asignificantly large number of air layers. Due to the fiber webframework, the elasticity, recovery rate and cohesive strength of thefiber web are improved without reducing the fundamental properties ofthe fiber web, and thus the fiber web can be used as a sound absorptionmaterial or a thermal insulation material.

Furthermore, the melt-blown fiber web has a high compression recoveryrate and a reduced weight, compared to conventional sound absorptionmaterials (PU foam, PET felt, glass fiber, etc.), and also has excellentsound absorption performance. In addition, the melt-blown fiber webaccording to the present invention has improved cohesive strength, highshrinkage rate and deformation rate and excellent processability,compared to conventional melt-blown fiber webs.

DESCRIPTION OF REFERENCE NUMERALS USED IN DRAWINGS

-   -   3: spinning die; 3A; inside of orifice;    -   4A and 4B: high-temperature and high-velocity gas injection        holes; 5 and 100: staple fibers;    -   6 and 102: melt-blown microfibers;    -   100A: outer portion of staple fibers;    -   100B: inner portion (hollow portion) of staple fibers;    -   10: fiber supply unit;    -   11: melt-blown fibers; 12: fiber web; 13: collector;    -   14: winding machine;    -   15: stack pattern change unit;    -   101A and 101AA: spunbond nonwoven fabric.

1. A melt-blown fiber web comprising of thermoplastic resin, themelt-blown fiber web comprising 10 to 60 wt % of thermoplastic resinmicrofibers and 40 to 90 wt % of non-circular cross-sectional hollowconjugated staple fibers with respect to the total weight of themelt-blown fiber web.
 2. The melt-blown fiber web of claim 1, whereinthe non-circular cross-sectional hollow conjugated staple fibers have asingle fiber fineness of 1-50 denier and a hollow ratio of 10% orhigher.
 3. The melt-blown fiber web of claim 1, wherein the non-circularcross-sectional hollow conjugated staple fibers are polygonal or tubularin cross section or have a protrusion/depression pattern at an outercircumferential portion thereof, and have an enlarged specific surfacearea.
 4. The melt-blown fiber web of claim 1, which comprises ahorizontal fiber layer and a vertical fiber layer formed on thehorizontal fiber layer, in which the horizontal fiber layer and thevertical fiber layer are continuously stacked and connected, and thevertical fiber layer is consisted of peaks and valleys, which have aheight of 2 to 50 mm and are arranged at irregular intervals.
 5. Themelt-blown fiber web of claim 4, wherein fibers at a top of the verticalfiber layer are entangled with one another to form an uppermost portionof a waved fiber web.
 6. The melt-blown fiber web of claim 1, whichfurther comprises a covering fabric consisting of a spunbond nonwovenfabric on an upper surface and lower surface of the melt-blown fiberweb.
 7. A method for producing a melt-blown fiber web, the methodcomprising the steps of: extruding a thermoplastic resin compositionthrough an extruder; spinning the extruded thermoplastic resincomposition together with a high-temperature and high-pressure gas toform thermoplastic resin microfibers; air-blending the thermoplasticresin microfibers with non-circular cross-sectional hollow conjugatedstaple fibers to form filaments; producing a melt-blown fiber web byforming one portion of the filaments into a horizontal fiber layer andconsecutively forming a vertical fiber layer on the horizontal fiberlayer by bringing the other portion of the filaments into contact with astack pattern change unit; and winding the produced melt-blown fiberweb.
 8. The melt-blown fiber web of claim 2, wherein the non-circularcross-sectional hollow conjugated staple fibers are polygonal or tubularin cross section or have a protrusion/depression pattern at an outercircumferential portion thereof, and have an enlarged specific surfacearea.